linux-kernel - Re: [PATCH v2] arm64/fpsimd: Only provide the length to cpufeature for xCR registers

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Message-ID: <ZNO6uh02/XxzhPAX@arm.com>
Date:   Wed, 9 Aug 2023 17:11:38 +0100
From:   Catalin Marinas <catalin.marinas@....com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Will Deacon <will@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arm64/fpsimd: Only provide the length to cpufeature
 for xCR registers

On Fri, Aug 04, 2023 at 05:37:25PM +0100, Mark Brown wrote:
> On Fri, Aug 04, 2023 at 05:20:21PM +0100, Catalin Marinas wrote:
> > On Thu, Aug 03, 2023 at 06:44:24PM +0100, Mark Brown wrote:
> > > On Thu, Aug 03, 2023 at 05:39:38PM +0100, Catalin Marinas wrote:
> > > > Maybe that's the simplest fix, especially if you want it in stable, but
> > > 
> > > Yeah, it's definitely the sort of change we want as a fix - anything
> > > more invasive would be inappropriate.
> > 
> > I'd say it's still ok if we can just rip come code out safely (the fake
> > ID reg).
> 
> It's the safely bit that concerns me here - it feels like a great way to
> discover why the code was there, possibly including a use that was there
> in the past but has subsequently been removed so bites a stable version.

As discussed earlier, let's queue this patch as is (for 6.6 I'd say)
with cc stable and post a new patch on top that removes the fake CPUID
register going forward, in case we missed anything.

For this patch:

Reviewed-by: Catalin Marinas <catalin.marinas@....com>